Wood Fillers

Let’s face it, woodworking blemishes—dents, scratches,
holes, and tear-out—happen. The trick is finding
the filler that, when
correctly applied, can make defects disappear.

There are dozens of different patching products, but most
fall into one of three general categories: solvent-based, water-based, and
two-part epoxies. Choosing the right filler
depends on several factors, including drying time, the size and type of repair,
and the kind of finish
you intend to apply.

Solvent-based

Solvent-based fillers
dry fast—most can be sanded within 15 minutes after application—and are
compatible with most finishes.
They’re the perfect choice when you want to fill
holes, sand them flush,
and then apply a finish
on the same day. Solvent-based fillers
shrink and crack less than their water-based counterparts. They’re also
suitable for exterior use.

On the downside, solvent-based fillers don’t accept stain well. They also tend
to be stiff and can be tricky to apply on larger areas. In addition to odor and
flammability issues,
cleanup requires a solvent—typically lacquer thinner. Because of its fast-drying
ingredients, this type of filler
tends to dry out in the can. Therefore, to prevent waste, buy solvent-based fillers in small quantities.

Water-based

Water-based fillers
dry fairly slowly—often taking 30 to 45 minutes. The extra working time and
smoother consistency mean they’re easier to tool, making them a good choice for
larger repairs or those that need shaping. Once dry, they are compatible with
most finishes and accept
stain well. Of course, water-based fillers
have no solvent odor and are nonflammable.
Some you can cut with water for use as pore fillers
on open-grained woods.

Water-based fillers
shrink more than solvent-based and sometimes crack. With a small investment in
time, you can apply a skim coat over the cracks and sand smooth.

Most water-based fillers
are soft, which makes for easy sanding, but this also means that they lack
structural integrity and may fail in areas that might see heavy use—like on a
tool handle or along a table edge.

Premixed fillers
have a longer shelf life than solvent-based, but should be protected from
freezing temperatures. Powdered fillers
work and perform similarly to Plaster of Paris. Setting-type putty has an indefinite shelf life, but once
mixed it hardens quickly. Both types can be tinted with water-based paints and
stains.

Many fillers claim to be stainable, but none accept stain
exactly like the surrounding wood. For the best patch, stain the piece and then
pick a filler (or stain a neutral filler) to match.

Tip Alert: Resist
the urge to mix sawdust and yellow glue. The blend seldom accepts finish and
can usually be spotted from across the room.

Two-part fillers

Ounce for ounce, two-part fillers
cost more, but when needed, they’re worth every cent. For a paint-grade patch,
epoxy putties are a good choice for rebuilding edges that will be shaped or are
likely to receive wear. Liquid epoxies do well at filling knots and cracks. Neither shrinks while
curing. Epoxies don’t accept stain, but you can add fine sawdust or universal pigments to obtain a perfect
match. Finally, epoxy has a long shelf life, but once mixed, you must use it
before it starts to cure and discard what you don’t use.